Background

Tissue hypoperfusion

An open gate for complications?

Organ hypoperfusion and reduced tissue oxygenation represent an  harmful condition frequently observed in critically-ill patients and during high-risk surgery. Shock state notably are characterized by an inadequacy between oxygen transport to parenchyma cells, and their need in oxygen to sustain normal organ function. This oxygen debt, if not corrected, is associated with increased organ dysfunction and poorer outcomes.
Additionally,  hemodynamic disturbances are prevalent during major surgical procedures and contribute to deterioration of proper perfusion of tissue.  In this regard, growing body of evidence hypothesizes that tissue perfusion alterations could play a pivotal role in the development of postoperative complications.

The economic burden of high-risk surgery

%
major complications [1]
%
of all perioperative deaths [2]
$
cost of complication per patient [3]
  1. Ghaferi, A., Birkmeyer, J., Dimick, J. (2009) Variation in hospital mortality associated with inpatient surgery. New England Journal of Medicine, 361(14), 1368-75
  2. Pearse RM, Harrison DA, James P, Watson D, Hinds C, Rhodes A, et al. Identification and characterization of the high-risk surgical population in the United Kingdom.Crit Care 2006;10:R81
  3. Michard, F., Mountford, W., Krukas, M., Ernst, F., Fogel, S. (2015) Potential return on investment for implementation of perioperative goal-directed fluid therapy in major surgery: a nationwide database study. Perioperative Medicine, 4, 11

Macro hemodynamics

Current approach for management of hemodynamics

To prevent complications associated with organ ischemia, clinicians pay a careful attention in monitoring and restoring optimal hemodynamic conditions for their patients.
Traditionally, the treatment strategy to ensure better oxygen delivery to cells consists in correcting macrohemodynamics derangements by administrating fluids and/or vasopressors, upon pressure-based resuscitation targets. Keeping track of cardiac output and preload-dependency, as well as monitoring of systemic hypoperfusion signals such as hyperlactatemia and/or central venous oxygen saturation, are common means to guide the therapeutic manoeuvers and assess the response of patient to treatment.

Micro hemodynamics

Beyond the 'whole body' approach

Recent studies have shown that microvascular alterations could be observed in conditions like severe heart failure or among patients undergoing high-risk surgery. Moreover, extensive literature have highlighted that, in septic shock, microvascular alterations often persist despite an increase of systemic blood flow within satisfactory levels and arterial blood pressure normalization. Therefore, the use of ‘global markers’ alone (Cardiac Output, Mean Arterial Pressure…) are not sufficient to monitor tissue hypoperfusion and could thus lead to suboptimal management of patient. Indeed, dissociation of macro- and microcirculation represents a peculiarly risky situation, in which physician could over emphasize the importance of arterial blood pressure and be falsely reassured that the patient is clinically stable. Furthermore, targeting merely systemic hemodynamics could even carry the risk of overusing vasoactive drugs that would worsen tissue perfusion.

Monitoring microcirculation

An unmet medical need

Thus far, continuous and real-time assessment of microcirculation at bedside was still challenging. Laser Doppler or Sidestream Dark Field imaging devices are mostly used for research purposes and could render “snapshots” of capillary perfusion, but cannot be considered as genuine monitoring solutions. Moreover, assessing tissue perfusion under the tongue remains controversial to faithfully provide an accurate picture of microperfusion. Hence, an easy & realistic way to continuously monitor tissue perfusion would address an unmet medical need both in intensive care medicine and anesthesiology.

Last update : 02/08/2019

microcirculation2